The present invention relates generally to food waste disposers and, more particularly, to a food waste disposer having a variable speed motor such as a switched reluctance machine.
The fineness and duration of grinding food waste are important considerations in the design and operation of a disposer. Many conventional food waste disposers use a single speed induction motor that rotates a grinding plate to grind food waste. The rotational speed of the grinding plate for most food waste disposers is between 1700 and 1800 rotations per minute (RPM). A food waste disposer having an induction motor is disclosed in U.S. Pat. No. 6,007,006 (Engel et al.), which is owned by the assignee of the present application and incorporated herein by reference in its entirety.
It has been found that the selected rotational speed of the grinding plate may affect the grind performance of the disposer for certain types of foods. For example, harder food particles such as carrot fragments and bone fragments may xe2x80x9cridexe2x80x9d on the grinding plate at high rotational speeds. Riding occurs when food particles rotate at the same speed as the grinding plate without being ground. Riding results in increased noise and vibration, as well as, residual food left in the grinding chamber after the disposer is turned off. Over time, residual food may cause unpleasant odors. Thus, a need exists for a food waste disposer having a mechanism to ensure all food is removed from the grind chamber.
Reduced flow in drain pipes is another important consideration in the design of a food waste disposer. A grinding chamber of a food disposer may be filled with food before the disposer is turned on by the user. For example, a user may fill the grinding chamber with potato peels before activating the disposer. When the conventional food waste disposer is turned on and immediately directed to a high rotational speed, a large slug of food may be forced down the discharge or drainpipe. This may reduce drain flow. Thus, a food waste disposer is needed that can prevent a large slug of food waste from being forced down the drainpipe during startup.
Another area of concern with conventional disposers is noise and power consumption. The typical rotational speed of the grinding plate for conventional disposers is fixed at a relatively high speed. Higher rotational speeds may produce more noise and consume more power. There may be times where the disposer is not grinding food but still turned on and running. For example, if a user is cleaning off the dinner table, there may be times when the disposer is running but no food is in the disposer. It would be beneficial to reduce the speed caused during periods of inactivity. Thus, there is a need for a disposer that reduces speed and power consumption during times of inactivity.
A further problem in designing a food waste disposer is jamming. Food waste in a conventional food waste disposer is forced by lugs on a rotating grinding plate against teeth of a stationary shredder ring. Jamming occurs when hard objects such as bones enter the food waste disposer and get stuck between the lugs of the rotating grinding plate and the stationary shredder ring. The prior art has tried to solve jamming by using motors that can be manually switched to rotate in the opposite direction. There is a need, however, for a food waste disposer that can automatically correct itself if a jam has occurred.
The present invention is directed to overcoming, or at least reducing the effects of, one or more of the conditions set forth above.
To that end, the present invention provides a food waste disposer having an upper food conveying section, a motor section, a central grinding section and a controller. The upper food conveying section includes a housing forming an inlet to receive food waste. The motor section includes a switched reluctance machine having a rotor and a stator. The rotor imparts rotational movement to a rotatable shaft. The central grinding section is disposed between the food conveying section and the motor section. The food conveying section conveys food waste to the grinding section. The grinding section includes a grinding mechanism where a portion of the grinding mechanism is mounted to the rotatable shaft. The controller is electrically connected to the stator to control the switched reluctance machine. The controller is capable of directing rotational movement to the rotatable shaft and the portion of the grinding mechanism mounted to the rotatable shaft. The controller is further capable of maintaining the rotational movement of the rotatable shaft at more than one rotational speed and direction.
The grinding mechanism of the food waste disposer may include a shredder plate assembly and a stationary shredder ring. In such an embodiment, the shredder plate assembly is the portion of the grinding mechanism mounted to the rotatable shaft. The shredder plate assembly may include fixed grinding lugs or moveable lugs.
In a further embodiment, the present invention includes a food waste disposer having an upper food conveying section, a motor section, a central grinding section, and a controller. The motor section includes a variable speed motor having a rotor and a stator. The rotor imparts rotational movement to a rotatable shaft that turns a portion of a grinding mechanism that is located in the central grinding section. The controller is electrically connected to the stator to control the variable speed motor. The controller is capable of operating in a variety of modes including soft start mode, optimized grinding mode, idle mode, rinse mode, and anti-jamming mode. For example, in one embodiment of the soft start mode, the controller is capable of activating the variable speed motor at startup to rotate a portion of the grinding mechanism mounted to the rotatable shaft and slowly increase the rotational speed of the portion of the grinding mechanism to a predetermined rotational rate over a predetermined period of time. In one embodiment of the optimized grinding mode, the controller is capable of rotating the portion of the grinding mechanism mounted to the rotatable shaft at a first rotational speed during a first period of time and rotating the portion of the grinding mechanism at a second rotational speed during a second period of time. In one embodiment of the idle mode, the controller is capable of rotating the portion of the grinding mechanism mounted to the rotatable shaft at a first rotational speed. The controller is further capable of determining whether food waste has entered the food waste disposer and increasing the first rotational speed to a second rotational speed if food waste has entered the food waste disposer. In one embodiment of the rinse mode, the controller is capable of rotating the portion of the grinding mechanism mounted to the rotatable shaft at a first rotational speed and increasing the first rotational speed to a second rotational speed during a period of time when water is introduced into the disposer. In this embodiment, the second rotational speed is greater than the first rotational speed. In one embodiment of the anti-jamming mode, the controller is capable of rotating the portion of the grinding mechanism mounted to the rotatable shaft at a first rotational speed and a first torque. The controller is further capable of determining whether food waste is jammed in the grinding mechanism by monitoring the current and speed provided to the variable speed motor and increasing the first torque to a second torque if it is determined that such a jam is about to occur or has occurred.
In another embodiment, the present invention includes various methods of operating a food waste disposer having a variable speed motor. The variable speed motor may be a switched reluctance machine or another type of variable speed motor. The operational methods include soft start mode, optimized grinding mode, idle mode, rinse mode, and anti-jamming mode. For example, in soft start mode there is a method for reducing a slug of food waste into a drainpipe by a food waste disposer. The food waste disposer has a variable speed motor, a rotatable shaft and a grinding mechanism. The variable speed motor imparts rotational movement to the rotatable shaft and a portion of the grinding mechanism that is mounted to the rotatable shaft. The method includes the steps of: activating the variable speed motor at startup to rotate the portion of the grinding mechanism that is mounted to the rotatable shaft; and slowly increasing the rotational speed of the portion of the grinding mechanism mounted to the rotatable shaft to a predetermined rotational rate over a predetermined period of time. The portion of the grinding mechanism mounted to the rotatable shaft may be a shredder plate assembly.
In an optimized grinding mode, there is a method of operating a food waste disposer having a variable speed motor, a rotatable shaft and a grinding mechanism. The variable speed motor imparts rotational movement to the rotatable shaft and a portion of the grinding mechanism that is mounted to the rotatable shaft. The method includes the steps of: rotating the portion of the grinding mechanism mounted to the rotatable shaft at a first rotational speed during a first period of time; and rotating the portion of the grinding mechanism mounted to the rotatable shaft at a second rotational speed during a second period of time. The second rotational speed is less than the first rotational speed. Moreover, the second period of time is after the first period of time. The first rotational speed may be between 2500 and 4000 rotations per minute. The second rotational speed is less than 2500 rotations per minute.
The method for operating in an optimized grinding mode may further include the step of rotating the portion of the grinding mechanism mounted to the rotatable shaft at a third rotational speed during a third period of time. The third rotational speed being less than the second rotational speed. The third rotational speed may be between 100 and 1500 rotations per minute.
In an idle mode, there is a method of operating a food waste disposer having a variable speed motor, a rotatable shaft and a grinding mechanism. The variable speed motor imparts rotational movement to the rotatable shaft and a portion of the grinding mechanism that is mounted to the rotatable shaft. The method includes the steps of: rotating the portion of the grinding mechanism mounted to the rotatable shaft at a first rotational speed; determining whether food waste has entered the food waste disposer; and increasing the first rotational speed to a second rotational speed if food waste has entered the food waste disposer. The first rotational speed may be between 400 and 800 rotations per minute although other relatively lower rotational speeds may be used.
The method for operating in idle mode may further include the steps of: determining whether food waste has exited the food waste disposer after increasing the first rotational speed to a second rotational speed; and decreasing the second rotational speed to the first rotational speed if food waste has exited the food waste disposer.
In a rinse mode, there is a method of operating a food waste disposer having a variable speed motor, a rotatable shaft, and a grinding mechanism. The variable speed motor imparts rotational movement to the rotatable shaft and a portion of the grinding mechanism that is mounted to the rotatable shaft. The method includes the steps of: rotating the portion of the grinding mechanism mounted to the rotatable shaft at a first rotational speed; entering water into the food waste disposer; and increasing the first rotational speed to a second rotational speed while entering water into the food waste disposer, the second rotational speed greater than the first rotational speed. The first rotational speed may be between 400 and 800 rotations per minute and the second rotational speed may be greater than 1500 rotations per minute. The entering of water may be through the same inlet as the food waste inlet or may be a separate means that automatically injects water into the disposer.
In the anti-jamming mode, there is a method of operating a food waste disposer having a variable speed motor, a rotatable shaft, and a grinding mechanism. The variable speed motor imparts rotational movement to the rotatable shaft and a portion of the grinding mechanism that is mounted to the rotatable shaft. The method includes the steps of: rotating the portion of the grinding mechanism mounted to the rotatable shaft at a first rotational speed and a first torque; determining whether food waste is jammed in the grinding mechanism by monitoring the current provided to the variable speed motor; and increasing the first torque to a second torque if it is determined that food waste is jammed in the grinding mechanism. Additionally, if it is determined that food waste is jammed, the rotation of the grinding mechanism may be reversed or, alternatively, a series of quick backward and forward rotations may be performed.
The method for operating in anti-jamming mode may further include the steps of: stopping the rotation of the portion of the grinding mechanism mounted to the portable shaft; and rotating the portion of the grinding mechanism mounted to the rotatable shaft in an opposite direction. Additionally, if it is determined that a jam exists, the rotatable shaft may be instructed to perform a series of quick backward and forward rotations to dislodge the jammed object.
The above summary of the present invention is not intended to represent each embodiment, or every aspect of the present invention. This is the purpose of the figures and detailed description which follow.